The invention concerns a process and a plant for the recovery of water from humid air, in which at night, humid air of lower temperature passes through a water storing adsorbent medium layer for the adsorption of water contained in the humid air and in which by day, air heated by means of solar energy and having a higher temperature which is higher than ambient temperature by day passes through the adsorbent medium layer for the desorption from the medium and adsorption by the air of the water extracted from the humid air by said layer at night. Subsequently the air is cooled for the condensation of the absorbed water which is conducted away after condensation.
This process will yield a relatively great amount of water if, among other things, the difference in temperature between the air passing through the adsorbent medium layer by day and the air passing through the adsorbent medium layer at night is large and if the air routed into the layer by day possesses a low relative humidity so that its absorption power for the water adsorbed by the adsorbent medium layer at night is correspondingly high.
A process is known from Offenlegungsschrift No. 26 24 392, in which at night humid air from the environment is passed first through a package of stones to be cooled by it and thereafter through a layer of silica gel seving as the adsorbing medium for the adsorption of water contained in the air. The silica gel is of a special type having an adsorption range between about 0.degree. and 20.degree. C. and a desorption range between about 25.degree. and 70.degree. C. Then, during the day, air from the environment is passed in reverse order first through the stone package cooled at night so that water adsorbed by the silica gel layer from the night air is extracted again by the air from the silica gel layer during the day and can be condensed on the stones, which have been cooled at night, and conducted away. Before entering the silica gel layer, the daytime air is heated by the adsorption of heat which is radiated by the surface of the silica gel layer, which is exposed to the sun rays, to a temperature which is above the outdoor temperature. The heating up of the air route into the silica gel layer to a higher temperature than the outdoor temperature is effected in the known process by passing the air between a translucent roof arranged above the silica gel layer and the surface of the silica gel layer which is exposed to the suns rays before it enters the silica gel layer. By this step, the so-called regenerative air is heated up to 52.degree. C. at a mean daytime temperature of the outside air of e.g., 40.degree. C. By taking suitable measures with the roof, a somewhat higher temperature of the regenerative air can be achieved.
This process known from the Offenlegungsschrift can be carried out only at places where the outdoor temperatures of the air at night are not above 20.degree. C. and it can be carried out economically only in those places where the differences in temperature of the outside air between day and night are large, since the heating up of the air routed into the silica gel layer, effected by solarization, causes only a relative small temperature rise.